I mean I wouldn't say it's semenatics. Folk punk is a distinct musical tradition that came out of post punk and has its roots in mainstream punk rock. Its like trying to call or The Eels Everclear an emo band. Like it's not wrong perse but it's definitely not right. Whereas built to spill, it would be correct to call them emo, or at least pre emo, and they were making music in that period.

Like, it's important to understand and respect that not all things are the same thing just because to our modern ear they sound similar, and now we would likely classify a group like Violent Femmes as folk punk. But folk punk didn't extend from violent femmes. It has different historical roots.